1. Field of the Invention
The present invention relates to a semiconductor memory device and, more particularly, to a semiconductor memory device for performing a high speed read-modify-write (hereinafter referred to as an RMW) operation for a large number of data.
2. Description of the Related Art
Demand has arisen for effectively writing image data in or reading image data from an image processing memory or the like and for effectively performing a high-speed RMW operation, i.e., the storage contents are read out from the memory, the read out data is modified, and the modified data is restored in the memory. A typical RMW application is exemplified by color inversion for inverting a color currently displayed on a display unit with a given relationship and providing pattern emphasis emphasizing a specific pattern.
A conventional RMW scheme is applied in such a manner that data is read out using an RMW function of a dynamic-random access memory (D-RAM) device, the read out data is modified by an external circuit, and the modified data is restored in the corresponding memory cell. However, the conventional RMW scheme requires a relatively long processing time defined by the operating cycle of the D-RAM device, resulting in inconvenience.